The Mental Retardation and Developmental Disabilities Research Center (MRDDRC) at the Children's Research Institute (CRI) of Children's National Medical Center was established in August 2001. It involves consortiums with George Washington University (GW) and Georgetown University (GU). The MRDDRC supports clinical and translational research in brain development and function, and currently consists of an Administrative Core, four scientific cores (Study Design and Biostatistics, Cellular Neuroscience, Functional Neuroimaging, and Molecular Genetics), and a New Program Develop Project. In this supplementary application, the investigators request funding to develop a new Mass Spectrometry (MS) Core. This supplemental application for the remaining three years of the funding cycle would permit the development of a MS Core for proteomics and other state-of-the-art MS methods. The proposed core will have three components: 1) a proteomics matrix-assisted laser desorption ionization time of flight/time of flight (MALDI-TOF/TOF) MS component with multidimensional liquid chromatography front end for protein separation; 2) a tandem MS component for pharmacological and metabolic analyses; and 3) a quantitative metabolic profiling of stable-isotope labeled tracers component (LC-MS and GC-MS). The MS Core would serve 22 NIH-funded MRDDRC projects covering nine of the research scope areas promoted in the MRDDRC RFA. [unreadable] [unreadable]